Topic 6: Plant Adaptations Flashcards
Photosynthesis is the conversion of what?
Photosynthesis is the conversion of CO2 into sugars.
What is/are the dark reactions in photosynthesis?
Energy carriers are used to power the Calvin cycle. CO2 is fixed by rubisco in a 3 carbon compound in the Calvin cycle. simple sugars (like glucose) eventually formed.
The dark reaction is called what?
The dark reaction is called the C3 pathway. C3 pathway has a major drawback in that rubisco can bind O2 instead of CO2 causing photorespiration.
What should the CO2 concentrations be in the leaf compared to the air?
CO2 gas concentration should always be lower within a leaf relative to the air.
What is heat loss by convection? What is the rate of loss dependent on?
The transfer of heat from a solid body to a fluid body. Rate loss depends on the temperature difference between the leaf and the air.
What is heat loss by evaporation (transpiration)? What is the rate of loss dependent on?
Evaporation causes a loss of heat energy and temperatures drop due to evaporative cooling. Rate of loss depend on transpiration rate, linked to moisture levels and humidity in the air.
What is the boundary layer? What is the impacts of it?
A boundary layer is a layer of still air adjacent to the surface of the leaf. A boundary layer has a major impact on the rate of heat and water loss.
What are the implications of a thick boundary layer?
The thicker the layer, the slower the rate of water and heat loss.
The boundary layer is modified by?
Wind- reduces the size of the layer by allowing mixing of the air to occur (via turbulence)
leaf size/shape- strongly influences the dynamics of air flow and consequently the size of the boundary layer.
larger and smoother leaves form thick and more stable layer.
smaller and consulate form thinner and less stable layer.
What is cold hardiness? What are the three types of cold hardiness? Also describe what kind of strategy/ mechanism it is.
cold hardiness of a plant is an adaptation to prevent cold damage.
- accumulation of compounds (avoidance strategy): sugars and amino acids to lower freezing point go water (taking the freezing temp to about -10c).
- supercooling (avoidance strategy): anti freeze proteins preventing ice crystal growth (taking the freezing temp -35c).
- deep hardening (tolerance mechanism): changing membranes composition to pump water out of cells allowing ice to form between cells instead of within (taking the freezing temp to -50c).
In shade plants, what is the limiting factor for photosynthesis?
Light is a limiting factor.
Describe where shade plants invest their energy, and what the result of this is?
Shade plants invest mainly in light reactions to capture any available light. large investments in dark reactions are not needed.
results in low net rate of photosynthesis. cellular respiration also tends to be lower as less sugars are available (slower growth rate, but more efficiently).
Describe the morphological structure of shade leaves.
shade leaves generally have a higher surface area and are thinner.
shade leaves generally are less convoluted and more rounded.
Describe the physiological structure of shade leaves.
Shade leaves have a slightly greater investment in the light reactions and lower photosynthetic rate.
